Blower inlet volume and spin control



April 6, 1954 J. CASSIE 2,674,402

BLOWER INLET VOLUME AND SPIN CONTROL Filed Sept. 30, 1950 Patented Apr. 6, 1954 BLOWER INLET VOLUME AND SPIN CONTROL John Cassie, Dedham, Mass., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 30, 1950, Serial No. 187,767

3 Claims. 1

This invention relates to centrifugal fans, and relates more particularly to inlet boxes for such fans.

Rectangular inlet boxes are usually provided around the axial gas inlets to the bladed wheels of centrifugal fans for connection to the ducts which convey air or other gases to the fans. Louvres are usually provided in the inlets of the inlet boxes for controlling the volume of gas supplied to the fans. tially closed, they cause the gas passing them to spin in the direction of wheel rotation which results in a reduction of power consumption as well as a reduction in gas volume. A detailed explanation of the reason for this may be found in the H. F. Hagen Patent No. 1,846,863. This action is highly desirable since, if dampering action alone was relied upon for reducing gas volume, there would be no saving in power consumption.

In some fans however, especially those which have supply ducts connected at angles to the inlet boxes, spinning of the gas occurs in the inlet boxes even when the volume control louvres are wide open. This is undesirable, since when such spin occurs in the direction of wheel rotation, the fans cannot be operated at full capacity. Accordingly, it has been the practice to place fixed, spinstop sheets in such inlet boxes diametrically across the axial inlets to the wheels for removing the spin from the gas entering the wheels. My patent No. 2,344,456 discloses such a spin-stop sheet. Such sheets, of course, prevent the use of spin for enabling the fans to be operated with reduced power at reduced capacity.

This invention provides spin-stop dampers within an inlet box across the axial inlet to a fan wheel, which are movable with the spin inducing louvres in the inlet to the inlet box, whereby when the louvres are adjusted to wide open position, the spin-stop dampers are closed for preventing the gas entering the fan wheel from spinning, and when the louvres are adjusted towards closed position for providing spin, the spin-stop dampers are adjusted towards open position for permitting the spin to persist.

An object of the invention is to provide means in an inlet box of a fan for permitting the gas entering the fan wheel to spin, or alternatively to remove any spin in the gas entering the fan wheel.

Another and more definite object of the invention is to provide spin-stop dampers within an inlet box of a fan, connected to spin-inducing louvres in the inlet of the inlet box in such a manner that when the louvres are wide open, the

When such louvres are parspin-stop dampers are closed, and when the louvres are adjusted towards closed position, the spin-stop dampers are adjusted towards open position.

The invention will now be described with reference to the drawing, of which:

Fig. 1 is an end elevation, partially in section, of a centrifugal fan embodying this invention, with the inlet louvres wide open and the spin-stop dampers closed;

Fig. 2 is a side elevation, partially in section, of the fan, and

Fig. 3 is an end elevation, in section, of the inlet box and illustrates the inlet louvres and the spin-stop dampers as partially open.

The fan has the wheel Ill mounted on the rotary shaft II, and has the shroud [2 connecting with an axial outlet from the box and providing an axial inlet lit for the wheel.

The rectangular inlet box I 4 extends around the inlet l3, and has connected to its gas inlet, the gas supply duct i5, which as illustrated by Fig. l, is connected at an acute angle to the inlet box.

The inlet box has the rotary spin inducing louvres l6 pivoted therein, and which are interconnected for simultaneous adjustment by the cross-arm H, from their wide open position shown by Fig. 1, to closed position.

The rotary spin-stop dampers 18 extend across the inlet box with axes parallel the axis of the fan shaft and on a vertical, radial line between the shaft and the upper side of the inlet box. The dampers [8 are interconnected by the cross-arm I9 for simultaneous adjustment, and are connected by the linkage comprising the links 20, 2| and 22, to the rotary shaft 23 to which is attached the worm-gear 24, meshed with the gear 25, rotatable by the hand-wheel 26.

When the spin inducing louvres it are in their wide open position as illustrated by Fig. 1, the dampers [8 are in their fully closed position. In closed position, the dampers [8 act as the usual spin-stop sheet for removing any spin in the gas entering the axial inlet l3 of the fan wheel, and resulting, even though the louvres l6 are in a non-spin inducing position, from the angular position of the duct I5. Thus the fan is able to operate at full capacity.

When it is desired to operate the fan at reduced load, the louvres I6 are rotated by the hand-wheel 26 in a counter-clockwise direction, facing Fig. 1 of the drawing, an amount depending upon the degree of load reduction. This causes the gas passing the louvres to spin in a 3 clockwise direction. Simultaneously with this adjustment of the louvres, the linkage connecting them with the dampers 18 causes them to rotate in a counter-clockwise direction. This permits the gas to pass between the dampers, and permits the spin in the gas entering the fan wheel to persist, thus permitting the volume of gas moved by the fan to be reduced with an accompanying reduction in power consumption.

It is preferred that the spin-stop dampers approach open position at a rate faster than the inlet louvres approach closed position.

While one embodiment of the invention has been described for the purpose of illustration, it should be understood that the invention is not limited to the exact apparatus and arrangement of apparatus illustrated, as modifications thereof may be suggested by those skilled in the art, without departure from the essence of the invention.

What is claimed is:

1. An inlet box for a fan having a fan wheel on a rotary shaft, said box having a gas outlet arranged centrally around said shaft and having a gas inlet in one side thereof, comprising volume control louvres pivoted in said inlet and arranged when rotated towards closed position to impart spin to the gas entering said inlet, and arranged when rotated to full open position, to have substantially no effect on the gas entering said inlet, pivoted spin-stop dampers extending between said shaft and another side of said box,

and arranged when closed to extend from closely adjacent said shaft to closely adjacent said other side of said box for removing any spin in the gas passing through said outlet, and arranged when open to permit any spin in the gas passing through said outlet to persist, means connected to said louvres for adjusting said louvres towards open or closed positions, and means connected to said dampers for adjusting said dampers towards open or closed positions.

2. An inlet box as claimed in claim 1 in which the means for adjusting the louvres and the dampers is interconnected and arranged to adjust the dampers towards open position when the louvres are adjusted toward closed position.

3. An inlet box as claimed in claim 2 in which the dampers are pivoted at spaced points along a line radial to the center of the fan shaft.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,846,863 Hagen Feb. 23, 1932 2,048,049 Baenninger July 21, 1936 2,201,437 Kice May 21, 1940 2,344,456 Cassie Mar. 14, 1944 FOREIGN PATENTS Number Country Date 549,457 Great Britain Nov. 23, 1942 

